1. Field of the Invention
The present invention relates to an information processing apparatus capable of being powered by a rechargeable battery. More particularly, the present invention relates to adaptive methods and apparatus for controlling the charging and discharging of the battery.
2. Background
In recent years, small lightweight information terminals (or portable computers) have come into wide use. Such information terminals are ordinarily provided with rechargeable batteries which enable the information terminals to be used while being carried outdoors or in the field. Each of the batteries is charged by an AC power supply when the information terminal is connected to the AC power supply, and can drive the information terminal when the information terminal is disconnected from the AC power supply.
Various kinds of batteries such as nickel-cadmium batteries, nickel-hydrogen batteries and lithium-ion batteries are being used. Such batteries typically degrade due to repeated charging and discharging. For example, with a nickel-cadmium battery or the like, there is a memory effect problem due to repeated charging after partial discharge. With other types of batteries free of the memory effect, there is also a problem that a control circuit incorporated in the battery is incapable of suitably controlling the full charge capacity which changes as the battery experiences repeated charge and discharge cycles.
Various techniques relating to these known problems have been proposed. See, for examples, Published Unexamined Patent Application No. 9-233722, Published Unexamined Patent Application No. 9-205736, Published Unexamined Patent Application No. 2001-136673, Published Unexamined Patent Application No. 2002-315198, and Published Unexamined Patent Application No. 2002-223529.
Technologies have been used that automatically starts charging a battery of an information processing device without any direction from a user when the device is connected to an AC power supply. This conveniently eliminates the need for troublesome operations for recharging and allows a sufficient amount of power of the battery to be maintained as long as possible. However, the technology starts charging on connection to an AC power supply even if the remaining amount of battery power is so sufficient that charging is not required. Consequently, the number of recharges of the battery increases and therefore the battery may degrade sooner.
When a battery degrades, the full charge capacity of the battery is reduced. At this time, a control circuit incorporated in the battery changes the upper limit of the amount of charging on the basis of information on the number of charging/discharging cycles, the charge/discharge capacity and the battery terminal voltage for example for the purpose of preventing overcharging of the battery. In some cases, e.g., a case where a short charging/discharging cycle is repeated, however, there is a possibility that the actual full charge capacity and the upper limit of the amount of charging set by the control circuit will differ from each other as a result of accumulation of errors in information about the battery. A user may perform a regeneration process of repeating complete charging and complete discharging to reset the upper limit of the amount of charging set by the control circuit to the actual full charge capacity. A comparatively long time is required to perform the regeneration process, but it is difficult for the user to determine in advance whether the full charge capacity can be actually recovered by the regeneration process. The conventional art therefore entails a possibility of failure to suitably perform the regeneration process for enabling the battery to perform the essential function.
Therefore, an object of the present invention is to provide an information processing apparatus and related methods capable of solving the above-described problem. This object can be attained by a combination of features described in the independent claims in the appended claims. In the dependent claims, further advantageous examples of the present invention are specified.